Has anybody added an aftermarket alarm system? I am wondering if there are any alarm systems that will automatically lock the car a few minutes after you get out of it. Lots of times I park my Cayenne to go into the gym or a store and can't remember if I locked it.

 

Viper makes a remote start and a security system. Either one will let you lock/unlock your vehicle from a smartphone app over cellular or WiFi (so you don't have to be close to the car). Have not installed either in my Cayenne but have had both in all my other cars.